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Articles 5911 - 5940 of 10319
Full-Text Articles in Physical Sciences and Mathematics
Population Dynamical Behaviors Of Stochastic Logistic System With Jumps, Ruihua Wu, Ke Wang
Population Dynamical Behaviors Of Stochastic Logistic System With Jumps, Ruihua Wu, Ke Wang
Turkish Journal of Mathematics
This paper is concerned with a stochastic logistic model driven by martingales with jumps. In the model, generalized noise and jump noise are taken into account. This model is new and more feasible. The explicit global positive solution of the system is presented, and then sufficient conditions for extinction and persistence are established. The critical value of extinction, nonpersistence in the mean, and weak persistence in the mean are obtained. The path-wise and moment properties are also investigated. Finally, some simulation figures are introduced to illustrate the main results.
On A Generalization Of Kelly's Combinatorial Lemma, Aymen Ben Amira, Jamel Dammak, Hamza Si Kaddour
On A Generalization Of Kelly's Combinatorial Lemma, Aymen Ben Amira, Jamel Dammak, Hamza Si Kaddour
Turkish Journal of Mathematics
Kelly's combinatorial lemma is a basic tool in the study of Ulam's reconstruction conjecture. A generalization in terms of a family of t -elements subsets of a v -element set was given by Pouzet. We consider a version of this generalization modulo a prime p. We give illustrations to graphs and tournaments.
Frobenius-Like Groups As Groups Of Automorphisms, Güli̇n Ercan, İsmai̇l Şuayi̇p Güloğlu, Evgeny Khukhro
Frobenius-Like Groups As Groups Of Automorphisms, Güli̇n Ercan, İsmai̇l Şuayi̇p Güloğlu, Evgeny Khukhro
Turkish Journal of Mathematics
A finite group FH is said to be Frobenius-like if it has a nontrivial nilpotent normal subgroup F with a nontrivial complement H such that FH/[F,F] is a Frobenius group with Frobenius kernel F/[F,F]. Such subgroups and sections are abundant in any nonnilpotent finite group. We discuss several recent results about the properties of a finite group G admitting a Frobenius-like group of automorphisms FH aiming at restrictions on G in terms of C_G(H) and focusing mainly on bounds for the Fitting height and related parameters. Earlier such results were obtained for Frobenius groups of automorphisms; new theorems for Frobenius-like …
Hilbert Series Of The Braid Monoid Mb_4 In Band Generators, Zaffar Iqbal, Shamaila Yousaf
Hilbert Series Of The Braid Monoid Mb_4 In Band Generators, Zaffar Iqbal, Shamaila Yousaf
Turkish Journal of Mathematics
L. A. Bokut gave a Gröbner--Shirshov basis of the braid group B_n in band generators. Using this presentation and solving all the ambiguities we construct a linear system for irreducible words and compute the Hilbert series of the braid monoid MB_4.
A Cohen Type Inequality For Laguerre--Sobolev Expansions With A Mass Point Outside Their Oscillatory Regime, Edmundo José Huertas Cejudo, Francisco Marcellán Espanol, María Francisca Pérez Valero, Yamilet Quintana
A Cohen Type Inequality For Laguerre--Sobolev Expansions With A Mass Point Outside Their Oscillatory Regime, Edmundo José Huertas Cejudo, Francisco Marcellán Espanol, María Francisca Pérez Valero, Yamilet Quintana
Turkish Journal of Mathematics
Let consider the Sobolev type inner product \langle f, g\rangle_S = \int_0^{\infty} f(x)g(x)d \mu (x) + Mf(c)g(c) + Nf^{\prime}(c) g^{\prime}(c), where d\mu (x) = x^{\alpha} e^{-x}dx, \alpha > -1, is the Laguerre measure, c < 0, and M, N \geq 0. In this paper we get a Cohen-type inequality for Fourier expansions in terms of the orthonormal polynomials associated with the above Sobolev inner product. Then, as an immediate consequence, we deduce the divergence of Fourier expansions and Cesàro means of order \delta in terms of this kind of Laguerre--Sobolev polynomials.
Pseudosymmetric Lightlike Hypersurfaces, Sema Kazan, Bayram Şahi̇n
Pseudosymmetric Lightlike Hypersurfaces, Sema Kazan, Bayram Şahi̇n
Turkish Journal of Mathematics
We study lightlike hypersurfaces of a semi-Riemannian manifold satisfying pseudosymmetry conditions. We give sufficient conditions for a lightlike hypersurface to be pseudosymmetric and show that there is a close relationship of the pseudosymmetry condition of a lightlike hypersurface and its integrable screen distribution. We obtain that a pseudosymmetric lightlike hypersurface is a semisymmetric lightlike hypersurface or totally geodesic under certain conditions. Moreover, we give an example of pseudosymmetric lightlike hypersurfaces and investigate pseudoparallel lightlike hypersurfaces. Furthermore, we introduce Ricci-pseudosymmetric lightlike hypersurfaces, obtain characterizations, and give an example for such hypersurfaces.
On The Equivariant Cohomology Algebra For Solenoidal Actions, Ali̇ Arslan Özkurt
On The Equivariant Cohomology Algebra For Solenoidal Actions, Ali̇ Arslan Özkurt
Turkish Journal of Mathematics
We prove, under certain conditions, that if a solenoidal group (i.e. 1-dimensional compact connected abelian group) acts effectively on a compact space then the fixed point set is nonempty and H_G^*(X,Q) has a presentation similar to the presentation of H^*(X,Q) as proven by Chang in the case of a circle group.
Functionals Of Gasser--Muller Estimators, Petre Babilua, Elizbar Nadaraya, Grigol Sokhadze
Functionals Of Gasser--Muller Estimators, Petre Babilua, Elizbar Nadaraya, Grigol Sokhadze
Turkish Journal of Mathematics
The asymptotic properties of a general functional of the Gasser--Muller estimator are investigated in the Sobolev space. The convergence rate, consistency, and central limit theorem are established.
Sedimentary Record Of Mid-Miocene Seismotectonic Activity In The Sinop Peninsula, North-Central Turkey, Ayhan Ilgar
Sedimentary Record Of Mid-Miocene Seismotectonic Activity In The Sinop Peninsula, North-Central Turkey, Ayhan Ilgar
Turkish Journal of Earth Sciences
The middle Miocene shallow-marine siliciclastic succession in the Sinop Peninsula, north-central Turkey, bears a well-preserved sedimentary record of syndepositional deformation associated with the buried escarpment of an oblique-slip dextral reverse fault and attributed to seismotectonic activity. The deposition occurred in a marginal trough at the edge of a tectonically inverted retroarc foreland basin of the Central Pontides. The synsedimentary deformation involved contemporaneous shoreface deposits and their consolidated, weakly cemented littoral substrate. Deformation features include neptunian dykes, convolute stratification, plumose transposition structure, injection dykes, diapirs, and large sandstone blocks dislodged from the fault escarpment. The genetic sequence of deformation structures deciphered …
Chemistry Of Magmatic And Alteration Minerals In The Chahfiruzeh Porphyry Copper Deposit, South Iran: Implications For The Evolution Of The Magmas And Physicochemical Conditions Of The Ore Fluids, Morteza Einali, Saeed Alirezaei, Federica Zaccarini
Chemistry Of Magmatic And Alteration Minerals In The Chahfiruzeh Porphyry Copper Deposit, South Iran: Implications For The Evolution Of The Magmas And Physicochemical Conditions Of The Ore Fluids, Morteza Einali, Saeed Alirezaei, Federica Zaccarini
Turkish Journal of Earth Sciences
The Chahfiruzeh deposit is a newly discovered porphyry-style copper deposit in the southern part of the Cenozoic Urumieh-Dokhtar magmatic arc of Iran. Mineralization is associated with a Miocene quartz-diorite to quartz-monzodiorite porphyritic intrusion (Chahfiruzeh porphyry) intruded into older basaltic and andesitic lava flows and pyroclastic rocks. Alteration assemblages and alteration zoning, typical of porphyry copper deposits, are well developed. Mineralization occurs in quartz-sulfide stockworks and as sulfide disseminations in the porphyritic intrusion and the immediate wall rocks. Pyrite and chalcopyrite are the main hypogene sulfide minerals; bornite and molybdenite are rare. Representative magmatic and alteration minerals, including plagioclase, amphibole, biotite, …
Utilization Of Petrographic Analysis For Determination Of Petroleum Coke Mixtures, Selami̇ Toprak, Emi̇ne Sütcü, Fatma Jale Gülen
Utilization Of Petrographic Analysis For Determination Of Petroleum Coke Mixtures, Selami̇ Toprak, Emi̇ne Sütcü, Fatma Jale Gülen
Turkish Journal of Earth Sciences
This study was carried out on mostly imported, processed petrocokes, which are also commercially known as petcoke or petroleum coke. Petrocoke is imported in great amounts and is occasionally consumed domestically without conscientious thought. It is not a well-known material, though there is an idea of its genesis. The samples, their analysis, and their images are essential to be kept in mind for further investigations, since it is not an environmentally friendly material. Petrographic and chemical analyses were conducted on all samples. Trace element and FT-IR analyses were made on a few representative samples. It is possible to distinguish petrocokes …
Selective Catalytic Reduction Of Sulfur Dioxide By Carbon Monoxide Over Iron Oxide Supported On Activated Carbon, Guangjian Wang, Liancheng Bing, Zhijian Yang, Jiankang Zhang
Selective Catalytic Reduction Of Sulfur Dioxide By Carbon Monoxide Over Iron Oxide Supported On Activated Carbon, Guangjian Wang, Liancheng Bing, Zhijian Yang, Jiankang Zhang
Turkish Journal of Chemistry
The selective reduction of sulfur dioxide with carbon monoxide to elemental sulfur was studied over AC-supported transition-metal oxide catalysts. According to the study, Fe_2O_3/AC was the most active catalyst among the 4 AC-supported catalysts tested. By using Fe_2O_3/AC, the best catalyst, when the feed conditions were properly optimized (CO/SO_2 molar ratio = 2:1; sulfidation temperature, 400 °C; Fe content, 20 wt%; GHSV = 7000 mL g^{-1} h^{-1}), 95.43% sulfur dioxide conversion and 86.59% sulfur yield were obtained at the temperature of 350 °C. Catalyst samples were characterized by X-ray powder diffraction in order to relate the phase composition to the …
Stability Analysis Of Multimachine Thermal Power Systems Using The Nature-Inspired Modified Cuckoo Search Algorithm, Shivakumar Rangasamy, Panneerselvam Manickam
Stability Analysis Of Multimachine Thermal Power Systems Using The Nature-Inspired Modified Cuckoo Search Algorithm, Shivakumar Rangasamy, Panneerselvam Manickam
Turkish Journal of Electrical Engineering and Computer Sciences
The stability of modern interconnected thermal power systems is greatly affected by the presence of low-frequency inertial oscillations in the system, due to various forms of disturbances experienced. This paper provides an efficient damping solution to these oscillations based on nature-inspired modified cuckoo search algorithm-based controller design. The proposed controller design is formulated as a parameter optimization problem based on damping ratio and time-domain error deviations. The effectiveness of the proposed damping controller design is illustrated by performing the nonlinear time domain simulations of the test multimachine power systems under various operating conditions and disturbances. Moreover, an exhaustive comparative stability …
Reliability-Based Maintenance Scheduling Of Generating Units In Restructured Power Systems, Mahmud Fotuhi Firuzabad, Farrokh Aminifar, Abbas Shahzadeh
Reliability-Based Maintenance Scheduling Of Generating Units In Restructured Power Systems, Mahmud Fotuhi Firuzabad, Farrokh Aminifar, Abbas Shahzadeh
Turkish Journal of Electrical Engineering and Computer Sciences
Maintenance scheduling of generating units in restructured power systems is a collaborative and interactive process between independent system operators (ISOs) and generating companies (GENCOs). The ISO should comply with GENCO maintenance preferences subject to targeted system reliability levels. This process might be multistage since the admission of all initial unit outage requests may threaten system reliability. Hence, the ISO accepts some proposals and determines alternatives for the remaining units. The GENCOs are then allowed to confirm the alternatives or revise them. In this paper the ISO problem of generating unit maintenance scheduling is tackled. The objective function is to minimize …
Optimal Reactive Power Flow Solution In Multiterminal Ac-Dc Systems Based On Artificial Bee Colony Algorithm, Faruk Yalçin, Uğur Ari̇foğlu
Optimal Reactive Power Flow Solution In Multiterminal Ac-Dc Systems Based On Artificial Bee Colony Algorithm, Faruk Yalçin, Uğur Ari̇foğlu
Turkish Journal of Electrical Engineering and Computer Sciences
Active power loss optimization is one of the important goals in electrical power systems and it is provided by optimal reactive power flow (ORPF). In this study, a new approach for the solution of the ORPF in multiterminal AC-DC systems is proposed. This approach provides 3 main contributions. First, the convergence problem in the AC-DC power flow is solved. Second, the problem of getting stuck in local minima during the optimization process is overcome. Third, a better global optimum point is obtained for the ORPF. Active power loss optimization is implemented through the artificial bee colony (ABC) algorithm, which is …
Comparison Of Ais And Fuzzy C-Means Clustering Methods On The Classification Of Breast Cancer And Diabetes Datasets, Seral Özşen, Rahi̇me Ceylan
Comparison Of Ais And Fuzzy C-Means Clustering Methods On The Classification Of Breast Cancer And Diabetes Datasets, Seral Özşen, Rahi̇me Ceylan
Turkish Journal of Electrical Engineering and Computer Sciences
Data reduction is an indispensable part of pattern classification processes in many cases. If the number of samples is excessive, sample reduction or data reduction algorithms can be used for an effective processing time and reliable successive results. Many methods have been used for data reduction. Fuzzy c-means is one of these methods and it is widely used in such applications as clustering algorithms. In this study, we applied a different clustering algorithm, an artificial immune system (AIS), for the data reduction process. We realized the performance evaluation experiments on the standard Chainlink and Iris datasets, while the main application …
A Performance Comparison Of Linear And Nonlinear Control Of A Scig-Wind Farm Connecting To A Distribution Network, Mohamed Benchagra, Mohamed Maaroufi, Mohammed Ouassaid
A Performance Comparison Of Linear And Nonlinear Control Of A Scig-Wind Farm Connecting To A Distribution Network, Mohamed Benchagra, Mohamed Maaroufi, Mohammed Ouassaid
Turkish Journal of Electrical Engineering and Computer Sciences
This study presents a comparison of linear and nonlinear control to regulate the DC-link voltage and power factor correction of a wind farm equipped with squirrel cage induction generators (SCIGs), connecting to a 22-kV distribution network. Both active and reactive powers are employed in 2 independent control laws. The proposed control strategies are derived from the Lyapunov approach. The aim of the control is to maximize the generated power with the lowest possible impact in the grid voltage and frequency during normal operation and under the occurrence of faults. The nonlinear backstepping controller to be used for the control of …
Coherence Analysis On Thermal Effect For Power Cables Under Different Environmental Conditions, Sezai̇ Taşkin, Şahi̇n Serhat Şeker, Özcan Kalenderli̇, Murat Karahan
Coherence Analysis On Thermal Effect For Power Cables Under Different Environmental Conditions, Sezai̇ Taşkin, Şahi̇n Serhat Şeker, Özcan Kalenderli̇, Murat Karahan
Turkish Journal of Electrical Engineering and Computer Sciences
There are 2 important aspects of this research; these are the experimental study and the data analysis, which are based on coherence analysis. In this study, a low-voltage power cable is tested under 2 different environments, air and water, and the variations in temperature are measured for the conductor, the sheath parts of the cable, and the environment. The recorded test data are analyzed using such as coherence analysis. This in turn provides the means to determine the relationship among the sheath, conductor, and the environment. In conclusion, high correlated peaks in the frequency domain are used to determine the …
Modeling And Simulation Of Deadbeat-Based Pi Controller In A Single-Phase H-Bridge Inverter For Stand-Alone Applications, Tow Leong Tiang, Dahaman Ishak
Modeling And Simulation Of Deadbeat-Based Pi Controller In A Single-Phase H-Bridge Inverter For Stand-Alone Applications, Tow Leong Tiang, Dahaman Ishak
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a deadbeat-based proportional-integral (PI) controller for a stand-alone single-phase voltage source inverter using a battery cell as the primary energy source. The inverter system is simulated in MATLAB/Simulink. It consists of a lead acid battery, third-order Butterworth low-pass DC filter and AC filter, H-bridge inverter, step-up transformer, and a variety of loads, as well as its sinusoidal pulse-width modulation (SPWM) deadbeat-based PI controller. In this paper, 2 simulation case studies are carried out, which are the abrupt load changes from a 400 W resistive load to a 500 W resistive load, and from a 400 W resistive …
Optimal Fuzzy Load Frequency Controller With Simultaneous Auto-Tuned Membership Functions And Fuzzy Control Rules, Abas Ali Zamani, Ehsan Bijami, Farid Sheikholeslam, Bahram Jafrasteh
Optimal Fuzzy Load Frequency Controller With Simultaneous Auto-Tuned Membership Functions And Fuzzy Control Rules, Abas Ali Zamani, Ehsan Bijami, Farid Sheikholeslam, Bahram Jafrasteh
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, an auto-tuned fuzzy load frequency controller (FLFC)-based artificial bee colony (ABC) algorithm is developed to quench the deviations in the frequency and tie-line power due to load disturbances in an interconnected power system. Optimal tuning of membership functions (MFs) and fuzzy control rules is very important to improve the design performance and achieve a satisfactory level of robustness for a particular operation. In this work, to reduce the fuzzy system design effort and take large parametric uncertainties into account, a new systematic and simultaneous tuning method is developed for designing MFs and fuzzy rules. For this, the …
Adaptive Feedback Control For Linear Singular Systems, Azita Azarfar, Heydar Toossian Shandiz, Masoud Shafiee
Adaptive Feedback Control For Linear Singular Systems, Azita Azarfar, Heydar Toossian Shandiz, Masoud Shafiee
Turkish Journal of Electrical Engineering and Computer Sciences
An adaptive state feedback control approach for linear descriptor (or singular) systems is investigated in this paper, which makes the closed-loop dynamics of this class of systems regular, impulse-free, and stable. The proposed adaptive method is based on the Lyapunov theorem to ensure the admissibility of the descriptor system and it also provides the state tracking with the desired reference trajectory. First, a control law is generated to stabilize the equilibrium point of origin, and, after that, the method is extended to a state tracking controller. The presented controller not only gets the stable output tracking asymptotically but is also …
Increasing Key Space At Little Extra Cost In Rfid Authentications, Gökhan Dalkiliç, Mehmet Hi̇lal Özcanhan, Hafi̇ze Şen Çakir
Increasing Key Space At Little Extra Cost In Rfid Authentications, Gökhan Dalkiliç, Mehmet Hi̇lal Özcanhan, Hafi̇ze Şen Çakir
Turkish Journal of Electrical Engineering and Computer Sciences
Traditional authentication and key establishment protocols utilize nonce parameters as a means for message freshness, recent aliveness, and key derivation. Improving identity verification, increasing key space, or making secret updates more complex through nonces are not goals. Generating random numbers as nonces and not making the most out of them can be considered as a loss in resource stricken radio frequency identification (RFID) tags. By increasing the shared secrets slightly, a new functionality for the nonces is introduced, which makes the authentication and key establishment protocols of RFID systems more secure, in general. The proposed method contributes to the security …
A Web Laboratory Using Matlab Builder Ne For Computer Image Processing, Sezgi̇n Kaçar, Cüneyt Bayilmiş, Özdemi̇r Çeti̇n
A Web Laboratory Using Matlab Builder Ne For Computer Image Processing, Sezgi̇n Kaçar, Cüneyt Bayilmiş, Özdemi̇r Çeti̇n
Turkish Journal of Electrical Engineering and Computer Sciences
Many various instruments are needed for computer image processing. These instruments are used for image restoration, analysis, etc. This paper presents a novel web laboratory based on MATLAB Builder NE with Web Figure, called ImageWeb, to facilitate computer image processing without needed technical information for users. The developed ImageWeb provides fundamental principles of image processing, including basic, compression, edge detection, filtering, optimization, and histogram processes, and so on. In addition, the usage of MATLAB Builder NE with MATLAB Web Figure provides high flexibility with visualization means such as zoom, rotate, and 3-dimensional view. Users can easily access ImageWeb using only …
A New Approach In The Evaluation Of Hospital Information Systems, Güney Gürsel, Neşe Zayi̇m, Kemal Hakan Gülkesen, Ali̇ Ari̇foğlu, Osman Saka
A New Approach In The Evaluation Of Hospital Information Systems, Güney Gürsel, Neşe Zayi̇m, Kemal Hakan Gülkesen, Ali̇ Ari̇foğlu, Osman Saka
Turkish Journal of Electrical Engineering and Computer Sciences
Hospital information system (HIS) evaluation frameworks have largely been discussed in the literature. However, existing frameworks lack one important aspect: to what extent user expectations of HISs are met. In this study, user expectation data are collected by means of the 'expectation questionnaire'. The internal consistencies of the answers to the questionnaire are measured by Cronbach's alpha coefficient. Fuzzy logic methodologies are used to evaluate the expectation variables in the proposed evaluation framework. The evaluation variables are not represented in the results equally; they are reflected by the weights assigned by the users. Our proposed framework provides the overall degree …
Spatiotemporal Realization Of An Artificial Retina Model And Performance Evaluation Through Isi- And Spike Count-Based Image Reconstruction Methods, İrfan Karagöz, Mustafa Özden
Spatiotemporal Realization Of An Artificial Retina Model And Performance Evaluation Through Isi- And Spike Count-Based Image Reconstruction Methods, İrfan Karagöz, Mustafa Özden
Turkish Journal of Electrical Engineering and Computer Sciences
Development of an artificial retina model that can mimic the biologic retina is a highly challenging task and this task is an important step in the development of a visual prosthesis. The receptive field structure of the retina layer is usually modeled as a 2D difference of Gaussian (DOG) filter profile. In the present study, as a different approach, a retina model including a 3D 2-stage DOG filter (3D-ADOG) that has an adaptively changing bandwidth with respect to the local image statistic is developed. Using this modeling, the adaptive image processing of the retina can be realized. The contribution of …
Markovian Approach Applied To Reliability Modeling Of A Wind Farm, Mazaher Hajibashi, Akbar Ebrahimi
Markovian Approach Applied To Reliability Modeling Of A Wind Farm, Mazaher Hajibashi, Akbar Ebrahimi
Turkish Journal of Electrical Engineering and Computer Sciences
The exploitation of wind energy as a resource for generating electricity is going to make a leap forward. Large-scale wind farms (WFs) will be engaged with power systems in the near future and this will cause changes in the supply pattern. Wind speed has an intermittent behavior and the output power of a WF is highly variable, consistent with this fact. The Markov process could consider this characteristic of wind speed using the state transition rate probability matrix, an issue that is neglected when a probability distribution function is established to model the wind speed data. The adequacy indices of …
Current-Mode Universal Filter And Quadrature Oscillator Using Cdtas, Jie Jin, Chunhua Wang
Current-Mode Universal Filter And Quadrature Oscillator Using Cdtas, Jie Jin, Chunhua Wang
Turkish Journal of Electrical Engineering and Computer Sciences
A current differencing transconductance amplifier (CDTA)-based multiple-input single-output (MISO) current-mode universal filter and a quadrature oscillator (QO) are presented in this paper. The same circuit is used in the filter and oscillator, which only consists of 2 CDTAs and 2 capacitors. The universal filter can realize low-pass, high-pass, band-pass, band-stop, and all-pass biquad filter functions. With a slight modification of the filter, a new current-mode QO can be obtained easily. The natural frequency and quality factor of the filter and the conditions of oscillation and frequency of oscillation of the QO are all orthogonally adjustable through the bias currents of …
Vessel Segmentation In Mri Using A Variational Image Subtraction Approach, Ayşe Nurdan Saran, Fati̇h Nar, Murat Saran
Vessel Segmentation In Mri Using A Variational Image Subtraction Approach, Ayşe Nurdan Saran, Fati̇h Nar, Murat Saran
Turkish Journal of Electrical Engineering and Computer Sciences
Vessel segmentation is important for many clinical applications, such as the diagnosis of vascular diseases, the planning of surgery, or the monitoring of the progress of disease. Although various approaches have been proposed to segment vessel structures from 3-dimensional medical images, to the best of our knowledge, there has been no known technique that uses magnetic resonance imaging (MRI) as prior information within the vessel segmentation of magnetic resonance angiography (MRA) or magnetic resonance venography (MRV) images. In this study, we propose a novel method that uses MRI images as an atlas, assuming that the patient has an MRI image …
Applications Of Wavelets And Neural Networks For Classification Of Power System Dynamics Events, Samir Avdakovic, Amir Nuhanovic, Mirza Kusljugic, Elvisa Becirovic
Applications Of Wavelets And Neural Networks For Classification Of Power System Dynamics Events, Samir Avdakovic, Amir Nuhanovic, Mirza Kusljugic, Elvisa Becirovic
Turkish Journal of Electrical Engineering and Computer Sciences
This paper investigates the possibility of classifying power system dynamics events using discrete wavelet transform (DWT) and a neural network (NN) by analyzing one variable at a single network bus. Following a disturbance in the power system, it will propagate through the system in the form of low-frequency electromechanical oscillations (LFEOs) in a frequency range of up to 5 Hz. DWT allows the identification of components of the LFEO, their frequencies, and magnitudes. After determining the energy components' share of the analyzed signal using DWT and Parseval's theorem, the input data for the classification process using a NN are obtained. …
How Do Hccmes Perform In Small Samples?, Mehmet Orhan, Esra Şi̇mşek
How Do Hccmes Perform In Small Samples?, Mehmet Orhan, Esra Şi̇mşek
Turkish Journal of Electrical Engineering and Computer Sciences
The purpose of this paper is to explore the performances of prominent and popular heteroscedasticity-consistent covariance matrix estimators (HCCMEs) in small samples. The HCCMEs are selected from the literature and their ability to estimate the true covariance matrix of the coefficient's vector is evaluated through simulation runs. We calculate the percentage difference between the expected value of the HCCME and the true covariance matrix to set a convenient stage to make the comparisons under several different regression settings. The main contribution of the paper is the inclusion of the HCCMEs that have been introduced into the literature recently. We report …